Melt seal

Abschmelzdraht, m. fuse wire, fusible wire. Vbschmelzeu, v.i. melt off, melt. fuse, separate by melting seal off, seal. — v.i. melt off. Abschmelz-konstante, /. fusion coeflScient. -achweissung, /, flash welding, -sicherung, /, (Elec.) safety fuse. 

The two apexes, where the two barrel lobes meet, are commonly truncated to promote axial mixing. The truncation ability eliminates some common fabrication and mechanical problems in twin-screw equipment. Finally, tight melt sealing is difficult to achieve, because of the open design features of the tangential TSEs. 

Polyesters, polyetherimide, melamine-formaldehyde, polyurethanes, polyurethane-ureas and polyamides (nylons) are examples of condensation polymers prepared by REX. " Because a small molecule is produced in condensation reactions, vent ports are employed. Between the ports are melt sealing screw sections, to prevent back mixing of volatilizing melt. Sealing screw sections are constructed by a right handed-left handed sequence of screw elements. Another chemistry feature of step-growth reactions is their sensitivity to errors in stoichiometric feed proportions. This poses problems with solid feed materials, which are normally converted to liquid form for more... 

After an extended period of time, some magnesium silicide will form on the walls of the heated glass tube. To avoid this, it is suggested that the Mg be placed in a tube of unglazed hard porcelain which is then inserted into a Pyrex or Vycor tube and melt-sealed to the latter at one end. With such an arrangement the Mg may even be heated to a somewhat higher temperature and its reactivity thus enhanced. 

Deuterium sulfide is introduced with shaking into an ice-cooled suspension of Ig in DgO placed in a closed recirculating glass apparatus with all joints melt-sealed. Unconverted DgS is reintroduced into the reaction mixture. The heavy hydriodic acid formed is separated from the precipitated sulfur by filtration (in the absence of air) and separated from the dissolved DsS by prolonged evacuation. 

After distillation is completed, the U-shaped storage vessel is melt-sealed at the bottom sections of the arms. Dioxygen difluoride can be stored only in liquid nitrogen. In emergencies. Dry Ice may be used. 

Sulfuryl bromide fluoride is stored by melt-sealing in quartz ampoules. 

Preparation by rapid aging at moderate temperature under CO 2 pressure 10 ml. of a cone, solution of ZnCls is frozen with Dry Ice in a freezing tube. A fourfold excess of solid KHCO3 and 10 ml. of H2O are added. A few pieces of Dry Ice are added on top and the tube is melt-sealed while still cold. It is kept at room temperature until the contents melt. The tube is then held at 130°C for two hours. 

A vertical bomb (wall thickness 3 mm., diameter 25 mm., height about 50 cm.) contains a solution of 10 mmoles of CdClg in 30 ml. of HgO, 0.3 ml. of cone, hydrochloric acid, and a small glass beaker filled with 20 mmoles of urea. A long stem from the bottom of the bomb supports the beaker above the liquid surface. The bomb is melt-sealed and heated at 200 °C for 18-24 hours. The yield is almost quantitative. 

Storage ampoules are first filled with N2 or CO 2 to avoid explosions during melt-sealing. To avoid the mipleasant results of shattering of the ampoules on explosion (flying glass, etc.), the ampoules should be stored in cotton wool Inside well-stoppered powder jars. 

These compounds are prepared by synthesis from the elements. The rare earth metal powder, as pure as possible, is placed in one of the arms of an L-shaped glass tube. The other arm contains the stoichiometric quantity of S, Se or Te (1 1 ratio). The tube is melt-sealed in vacuum and heated in an electric furnace until the non-metal is completely consumed. The temperature should reach 400-450 °C by the end of 2-3 days. Powder pattern analysis of the products indicates the formation of nonhomogeneous materials containing LngXa and LngX, but not LnX, which starts to form at1000-1100°C. 

Freshly distilled TiCU (28 g.) is placed in a bomb tube and the Sb (6 g.) is added the reactor tube is melt-sealed and heated for five hours at 340 °C. After cooling, both tube ends are broken off and the moist mass, in a stream of CO 3, is transferred to a three-neck flask via an adapter at neck a. Then CCU is added from a dropping funnel attached to neck b while the mixture is agitated with a stirrer inserted through the center neck this dissolves out the unreacted TiCU. The mixture is allowed to... 

Vanadium metal (turnings or powder) and excess 13 are placed in a hard glass or fused quartz tube, closed at one end the tube contents are cooled to — 80°C the tube is thoroughly evacuated and then melt-sealed to a short total length. A vigorous reaction sets in on heating. The entire tube is heated for a while at temperatures up to 300°C in order to achieve product uniformity. The excess I3 is then allowed to distill off into a somewhat cooler zone, and the tube is quickly cooled and opened. 

A thoroughly ground mixture of 3.6 g. of dry VsOs and 9.4 g. of VCI3 is placed at the closed end of a 1-m.-long tube, and 0.9 ml. of VOCl3 is then added. The upper part of the tube must be free of traces of these substances. The tube, filled with air, is melt-sealed, and is covered along its entire length with a sheet-metal jacket its... 

All vanadium sulfides can be S3mthesized from the elements. An intimate mixture of the finely pulverized components, in the proper proportions. Is placed in sintered clay tubular crucibles these are inserted in quartz tubes, which are then evacuated and melt-sealed. The tubes are then slowly heated and finally maintained for a long time at a maximum temperature of 1000-1300°C. Contact between the vanadium metal and the quartz must definitely be avoided. 

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